This invention relates to a roll sheet cassette loading apparatus for use in a copying or reproducing machine, in which a cassette containing therein a record sheet in the roll form is employed so as to facilitate the loading and exchanging the record sheet in and from the copying machine body.
In a prior art copying machine using a roll sheet, the procedure of loading a roll sheet in the copying machine and of exchange of one type roll sheet to another have been very complicated as follows; a rotary shaft is first inserted in a desired roll sheet; then the roll sheet and the rotary shaft is set in the copying machine, with the leading edge of the sheet being guided through complicated passages in the machine body so that the edge of the sheet is brought into the bite of the sheet feed rollers; and the sheet feed rollers are rotated by a given amount to feed the roll sheet to a given position. Such procedures, however, have been time consuming. Furthermore, during these procedures, fingerprints or stains of an operator would be left on the surface of the roll sheet and the operator is required to handle these procedures carefully so as not to fold or damage the end portion of the sheet during these procedures.
A roll sheet which is taken out from the copying machine body, for exchange of sheet size between an A-size sheet and a B-size sheet is liable to be stained on the surface thereof, as well as broken or folded in the end portion thereof.
The stains on the sheet surface or the undesired charge on the sheet would be undesirably developed into a visible image in an overlapped relation to a desired developed image of an original, particulary in the case where a sheet of zinc oxide or an electrostatic record sheet is used. The fold or break in the end portion of the sheet is responsible for the jamming of the sheet during the transportation thereof within the copying machine body.
In order to solve the above-described drawbacks, a variety of roll cassette type copying machines have been proposed, in which an A-size roll sheet and a B-size roll sheet are set in different cassettes, respectively, so that the cassette itself may be replaced by another at the time of exchange of one size sheet for another.
These prior art apparatuses, however, include a variety of problems, particularly from the practical viewpoint of the copying machine.
In the meantime, in most apparatuses of the prior art, roll-sheet-cassette loading mechanisms have been so arranged that replacement of one cassette with another is effected from one side of the copying machine body. In the case of replacing one cassette with another, an operator therefore must change his position from the front of the copying machine to one side of the machine body, since the operator is in front of the copying machine body normally in the event of operating the copying machine. This impairs ease of handling that is one of the advantages of a cassette type loading mechanism, and is inconvenient for handling the cassette itself. A copying machine, in many cases, is installed in an office having a narrow floor space, mostly at the corner portion of such an office. In such cases, it is required to keep a space larger than a space which is actually occupied by the copying machine itself on one side of the machine body, so as to afford replacement of one cassette with another from that side of the copying machine body.
Regarding the positioning of the leading edge of the record sheet in the roll form usually at a constant position, various attempts have hitherto been proposed: one is such as shifting the leading edge of the sheet to a position of a cutter by utilizing the shifting stroke of a cassette loading mechanism in association with the operation of mounting the roll sheet cassette in the copying machine body; and the other is such as locating the leading edge of the sheet at a proper position by separating one sheet feed roller on the copying machine side from another while the leading edge of the sheet is left as it is. In the former, the construction of the apparatus is complicated and precision in machining of mechanical portions is highly required in order to locate the leading edge of the sheet properly at a constant position. Furthermore, in order to mount the cassette in the copying machine body, an operator must pay a close attention to the condition of engagement between the cassette and a sheet feeding member in the copying machine body in the event of loading the cassette. This requires an experienced skill and hence partly impairs the advantages inherent in a cassette system. In the latter, the leading edge portion of the sheet is exposed over a comparatively long area from the cassette and remains unsupported. Such a long leading edge portion of the sheet must be inserted between the sheet feed rollers in the copying machine body, while the leading edge portion is maintained in a horizontal direction. In order to load or mount the cassette in the copying machine under such a condition, an operator is required to handle the cassette carefully, so that the leading edge of the sheet is fitted in a small gap between the feed rollers and that the leading edge portion thereof is not folded or broken. Thus, this latter case also failed to make the best use of the advantages of the cassette system.
Further, in more detail, problems arise in the event of replacement of one roll sheet cassette with another are how to locate the leading edge of sheet at a constant point precisely and how to protect the leading end portion thereof. Under a condition that a cassette is mounted and served for use in the copying machine body, the sheet extends from a sheet exit opening in the cassette, via a first sheet feed roller and locates its leading edge at a position of the cutter. In the case that the cassette is demounted from the copying machine body, and that thereafter the cassette is set again in the copying machine body for the following copying service, the leading edge of the sheet must be positioned always at the same position precisely in order to cut the roll sheet by a given length accurately even from the first copying operation. This is met by employing a method, in which a roller for drawing or putting the leading end of sheet out of or into a cassette is provided in the cassette, in a manner that the roller is rotated by utilizing the shifting stroke of the cassette with respect to the copying machine body when mounted or removed therein or therefrom, and when the cassette is removed from the copying machine body, the leading end of the sheet is submerged in the cassette so as to be protected from external force, and when the cassette is mounted in the copying machine body, the leading end of sheet is fed to the home position of the cutter. With this method, however, it is necessary to provide a mechanism by which the upper and lower sheet feed rollers provided in the copying machine body is spaced from each other simultaneously at the time of insertion or removal of the cassette in or from the copying machine body and these sheet feed rollers rotate simultaneously at the time of feeding the sheet. This results in the complexity in construction as a whole, the need for a high precision in machining of respective portions in order to realize reliable operations, leading to a costly device. To cope with this, another attempt has been proposed, in which a cassette is mounted in or removed from the copying machine body only by separating one sheet feed roller from the other on the machine body side, while the leading end of sheet remains intact. With this method, the leading end of sheet is left as it projects long from the cassette when removed from the copying machine body and is likely to be subject to a damage such as being folded or broken. In the case of mounting the cassette in the copying machine body, a close attention is required for inserting the leading end of the sheet in a small gap between the feed rollers in the copying machine body. Since the cassette itself does not include any means, such as a roller, for supporting the leading end of the sheet, it is possible that due to shock or vibration upon handling of the cassette, the roll sheet is unwantedly rotated to submerge the leading end in the cassette, and therefore it is difficult to restore the leading end of the sheet to the home position.